The concept of drug targeting has gained importance in recent years, especially for anticancer drugs, inasmuch as toxic side effects of anticancer drugs to normal cells are a primary obstacle in cancer chemotherapy due to lack of selectivity to cancer cells. Drug targeting can be accomplished by conjugation with, or encapsulation in a specific transporter to the target. Materials such as proteins, saccharides, lipids and synthetic polymers have been used for such transporters. Antibodies have been perhaps most widely used due to their target specificity and wide applicability.
Yokohama et al, Makromol. Chem. 190, 2041-2054 (1989) describe adriamycin conjugated with immunoglobulin G using polytethylene glycol)-block-poly(aspartic acid) as a carrier. The adriamycin is bound to the poly(aspartic acid) chain and immunoglobulin G is attached to the poly(aspartic acid) via disulfide linkages.
Recently, substances substituted with PEG chains for treating or diagnosing tumors have been described in PCT/EP91/00992. However, there is no suggestion of a polymer containing units comprising a poly(alkylene oxide) moiety linked to a chelating agent.
It is apparent that it would be desirable to provide new classes of materials having a specificity toward accumulation in different tissues, and which remain in the blood pool for long periods of time.